Investments - Schedule of Total Investments (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Total Investments [Line Items]
Current	$ 2,373	$ 2,522
Long-term	17,314	15,732
Total	19,687	18,254
Debt securities available for sale
Total Investments [Line Items]
Current	2,251	2,359
Long-term	14,671	12,896
Total	16,922	15,255
Mortgage loans
Total Investments [Line Items]
Current	122	145
Long-term	1,091	1,216
Total	1,213	1,361
Other investments
Total Investments [Line Items]
Current	0	18
Long-term	1,552	1,620
Total	$ 1,552	$ 1,638